Electric switch



NOV. 14, v STIMSQN 2,352,855

ELECTRIC SWITCH Filed Nov; 22, 1941 Inventor: Allen GStimson,

His ttorney.

j UNITED, STATES PATENT OFFICE 2,362,855 npnc'rmc swrron Allen G;Stimson,

General Electric Company,

New York Marblehead, Masa, assignor to a corporation of ApplicationNovember 22, 1941, Serial No. 420,107

Claims. (Cl. 260-166) My invention relates to electric switches, particularly electric switches provided with a contact which is subject torebound with consequent damaging arcing upon engagement with the othercontact, and has for its object simple and effective means forpreventing rebound of a switch contact upon engagement with anothercontact.

It is generally understood that failure of electric contacts is due toarcing and welding of the contacts. Furthermore, since the heat requiredfor noticeable welding can be produced only by arcing, and since arcingwill take place only if, the contacts rebound after initial en-=gagement, it follows that contact failures maybe eliminated or reduced'by preventing rebound of the contacts after their initial engagement.Rebound of contacts is a common impact phenomenon and is due to theconversion of'the kinetic energy of the moving parts into potentialenergy having a tendency to simply reverse the direction of motion ofthe moving parts if the impact is direct. Since the rebound velocity isa fixed percentage ofthe speed of approach, the percentage dependingonly upon the materials involved and not upon the mass of moving parts,the rebound is particularly vioj small snap with the fixed contact zero.By of the weight is permitted forces by building up a certain amount ofpotential energy by elastic strain in a direction having little tendencyto reopen the contacts. Ultimate dissipation of the potential energyinto internal friction or the like permits the weight to come to restwithout causing the contacts to rebound.

For a more complete understanding of my invention reference should nowbe had to the following detailed description taken in conjunction withthe accompanying drawing in which Fig. 1 is aside view of \an electricalcontact element embodying my invention in oneform; and Fig. 2 is asimilar view of the essential parts of an electrical cotact deviceembodying my invention in another form.

Referring now to Fig. 1, the embodiment of my invention illustratedtherein comprises a fixed contact l0 mounted upon a support I l adjacenta action magnet l2. For cooperation I0 I provide a movable" contact armcomprising a pivotally mounted end portion l3 carrying at its end anelongated spring strip It. The member I3 is shown pivotally mounted upona fixed knife-edge sup.-

lent where the speed of apporach is relatively p 1f A Su a m n y beProvided high. Thus, while the impact forces and confor actuating thecontact arm l3, I4 between sequent rebound may be reduced by reducingopen and closed circuit positions. In the form the speed of approach andhence the kinetic enshown the pivoted member I3 is of magnetic materialand forms a movable armature for comergy, this is impractical in certainapplications, for example, in snap acting devices or in elecpleting themagnetic circuit of an actuating tromagnetically actuated switches; Insuch apelectromagnet IS. The contact arm l3, M is plications it becomesnecessary to devise means tor converting the kinetic energy of themoving parts to some other form of energy having little or no tendencyto reopen the contacts. In general, the kinetic energy may be convertedinto either heat or other forms of work, potential energy such aselastic strain, electric energy, or kinetic energy in another direction.I

In carrying out my invention I provide. means for converting the kineticenergy of movin contact parts into elastic strain in a direction havinglittle or no tendency to reopen the contacts and then dissipating suchpotential energy into heat of internal friction or the like.

In one 'form' of my invention I resiliently mount a substantial'weight'uppn the movin contact member in such a way thatafter thecontacts come into engagementthe weight continues to move butthe-direction of motion of the weight is changed. Thus the kineticenergy of the movingparts is not immediately reduced to light tensionspring 11. spring strip ll biased into open circuit position by means ofa At its free end the carries a movable contact l8 for cooperation withthe fixed contact l0 and a magnetizable armature IQ for cooperation withthe snap action magnet l2.

Mounted upon the spring strip l4 intermediate its ends I provide aninertia member or weight 20 having a substantial mass relative'to themass of the contact arm itself. In the form shown the weight 20 ismounted upon a resilient, angle bracket 2| which is in turn attached asby welding to approximately the center of the spring strip l4. Due tothe inertia of the weight 20 the effective length of the contact springI4 is reduced to that distance between the movable contact and thepointof attachmentof the bracket 2| to the spring ll. This distance isindicated by the reference numeral 22,

In operation, when the actuating electromagnet It is energized toattract the armature l3 this means the continued movement to cushion theimpact merely tends and move the contact spring H into contact engagingposition all the moving parts move substantially in unison until thecontacts and 18 are engaged. Upon engagement of the contacts the kineticenergy of the moving parts is not immediately reduced to zero but theweight 28 continues to move against the bias of the springs l4 and 2|.Such continued movement of the weight 20, however, is a substantiallyfree rotary movement with respect to the point of attachment of thebracket 2! to the spring II. This rotation is due to the fact that thebracket 2| is equally or less resilient. than the spring i4 and supportsthe weight 20 in cantilever fashion. Thus the kinetic energy in theweight 20 is Q changed in direction and permitted to build up a certainamount of potential energy by twisting of the spring strip l4. Twistingof the spring l4 at its center caused by the rotary movement of theweight 20 tends to slide the contact 18 longitudinally to a smalldegree, but not to reopen the contacts. When the weight 20 is brought torest by elastic strain in the spring strip the potential energy in thespring strip 14 and the bracket 2| will reverse the movement of theweight 20 and twist the spring I 4 in the opposite direction, andoscillation of the weight 20 about the point of connection of thebracket I 2i to the spring strip M will continue until all the energy ofthe weight is dissipated in friction. However, the elastic strain in thespring strip i4 is in such a direction that the spring strip I l tostraighten longitudinally rather than to rebound laterally and reopenthe contacts. It is not contemplated that the weight 26 will engage thearm H above the contact 18.

At Fig. 2.1 have shown another embodiment of my invention in which thecontact arm comprisesa rigid lever 25 pivoted at a fixed point and arigid weighted contact lever 23 pivotally mounted upon the end of thelever 25. The rigid lever 25, or part of it, may be composed ofmagnetizable material to serve as a movable armature completing themagnetic circuit of an actuating electromagnet 2?. The lever 25 ispivotally mounted upon a fixed knife-edge pivot formed upon the magneticframe 28 of the magnet and is biased to a circuit opening position bymeans of a light tension spring 23. Preferably the free end of the rigidpivoted member 25 is formed to provide a knife-edge pivot 33 engagingthe contact lever 26 intermediate its ends. The contact lever 28 carriesat one end a movable contact 31 arranged to engage a fixed contact 32.At the opposite end of the contact lever 26 is disposed a substantialmass or weight 33. The contact lever 36 is disposed on the side of therigid lever 25 adjacent the fixed contact 32 in such a way that themovable contact 31 extends beyond the end of the lever 25. The members25 and 25 are connected together and biased into engagement by means ofa rivet or bolt 34 and a compression spring 35. The contact lever .23and the weight 33 are so designed that their integrated center ofgravity is located between the pin 34 and the weight 33, that; is, thecenter of gravity of the contact lever assembly is located on theopposite side of the pin 34 from the movable contact 3 I In operation,when the electromagnet 21 is energized the armature lever 25 is drawntoward the magnet in a'direction to close the contacts 3| and 32.Initially the entire contact arm, including the levers 25 and 23 and theweight 33, are moved as a unit. However, as soon as the contacts comeinto engagement, the contactcarrying 'end of the. contact lever 26 isbrought to rest while the weight 33 and the armature lever 25 continueto move. During this latter phase of the movement the armature lever 26and the weight 33 rotate about the point of engagement of the contacts3i and 32, thereby causing the weight 33 to move away from the armaturelever 25 and to compress the spring 35. Thus, the weight 33, initiallyrotating about the knife-edge pivot on the frame 28, is forced to changeits point of rotation after the contacts come into engagement so thatthe kinetic energy of the moving parts is not immediately reduced tozero but is changed in direction and gradually converted into elasticstrain in the spring 35. When recovery of the potential energy stored inthe spring 35 takes place the contact lever 26 and the weight 33 arforced to rotate in the opposite direction about the point of.engagement of the contacts so that there is no substantial tendency toreopen the contacts. Since the point of engagement of the contacts isthe center of rotation for the lever 26 and the weight 33, there is notendency to open or to slide the contacts.

While I have shown only certain embodiments of my invention by way ofillustration, many further modifications will occur to those skilled inthe art, and I therefore wish to have it understood that I intend by theappended claims to cover all such modifications as fall within the truespirit and scope of my invention. i

What I claim as new and desire to secure'by Letters Patent oi the UnitedStates is:

1. An electric contact making and breaking device comprising cooperatingswitch contacts, a

movable contact arm pivotally mounted at one end and carrying one ofsaid contacts at its other end, a relatively movable weight carried bysaid contact arm, said weight having a mass sub stantial with respect tothe mass of said arm, means including a resilient member for connectingsaid weight to said arm, and means for moving said arm to engage anddisengage said contacts, said connecting means being arranged to permitappreciable free arcuate movement of said weight after engagement ofsaid contacts and about said contacts as a center after engagement ofsaid contacts thereby to convert the kinetic energy or said weight arminto elastic strain having no-substantial tendency to disengage saidcontacts or produce relative sliding movement thereof.

2. An electric contact making and, breaking device comprisingcooperating switch contacts, a

movable contact arm pivotally mounted at one end and carrying one ofsaid contacts at the other end thereof, a weight movable with said armand having a mass substantial with respect to the mass of said arm,resilient means for pivotally mounting said weight upon said arm, meamfor I moving said contact arm to engage said con tents, and means forconstraining said weight to rotate freely about the point of engagementof said contacts after their engagement thereby to stress'said resilientmeans and to convert the kinetic energy of said contact arm into elasticstrain in said resilient means, said strain being so directed that ithas no substantial tendency to reopen said contacts.

3. An electric contact making and breaking device comprising a fixedcontact, a movable switch arm including a rigid member pivotally mountedat one end and a weighted contactlever resiliently connected to theother end of ed to said rigid arm at a point intermediate said movablecontact and the center of gravity of said contact lever, and means formoving said rigid member to engage said contacts, whereby when saidcontacts engage said contact leverpivots about the point of engagementof said contacts thereby to change the path of' travel of said lever andto convert the kinetic energy of said switch arm into elastic strainhaving no substantial tendency to disengage said contacts and having notendency to produce relative sliding movement of said contacts.

4. An electric contact making and breaking device comprising a fixedcontact, a movable switch arm including a movably mounted rigid memberand a weighted contact lever pivotally connected to said rigid member,said contact 1ever carrying at one end thereof a movable contactarranged to engage said fixed contact and being pivotally connected tosaid rigid member at a point intermediate said movable contact and thecenter of gravity of said contact lever, resilient means connectedbetween said contact lever and said rigid member for biasing saidmembers to a predetermined relative position, stop means for determiningsaid predetermined position, and, means for moving said switch arm toengage said contacts, whereby when said contacts engage said contactlever rotates relative to said rigid member and against the bias of saidresilient means thereby to change the path of travel of said lever andto convert the kinetic energy of said switch arm into elastic strainhaving no substantial tendency to disengage said contacts. I I

5. An electric contact making and breaking device comprising a fixedcontact, a. movable switch member, a contact lever pivotally connectedto said movable switch member, said con-- tact lever having asubstantial mass and carrying at one end thereof a movable contactarranged to engage said fixed contact, said pivotal connections beingpositioned intermediate said movable contact and the center of gravityof said contact lever, resilient means for biasing said contactv leverto a predetermined fixed position with respect to said switch member,and means for moving said switch member to engage said contacts, wherebysaid contact lever ,moves with said switch member until said contactsengage and thereafter .rotate relativ to said switch member against thebias of said resilient means thereby to convert the kinetic energy ofsaid switch member and contact lever into elastic strain having nosubstantial tendency to disengage said contacts. 6. An electric contact,making and breaking device comprising cooperating'switch contacts,

a resilient contact arm carrying on of said contacts at one end thereof,said arm being mounted for lateral movement between contact breaking andcontact making positions, an inertia member of substantial mass inrelation to the mass of said contact arm, and resilient cantileversupporting means for mounting said inertia member intermediate the endsof said contact arm in spacedv relation thereto for appreciable freeovertravel with respect to said arm after engagement of said contacts,said overtravel being a substantially arcuate movement about the fixedend of said cantilever supporting means thereby to convert the kineticenergy of said contact arm into elastic strain in a direction having nosubstantial tendency to reopen said contacts.

'7. An electric contact making and breaking device comprisingcooperating switch contacts, a resilient contact arm carrying one ofsaid contacts at one end and being pivotally mounted at the other endfor movement between circuit breaking and circuit making positions, aninertia member of substantial mass in relaton to the mass of sad contactarm, offset resilient cantilever supporting means having a portionextending in substantially parallel spaced relation with respect to saidcontact arm for mounting said inertia member intermediate the ends ofsaid contact arm for appreciable fre .overtravel with respect to saidcontact arm after engagement of said contacts, and means for moving saidcontact arm and said inertia member in unison from a contact breaking toa contact making position, said resilient cantilever supporting meanspermitting free'overtravel of said inertia member wth respect to saidarm after engagement of said contacts thereby to twist an intermediatesection of said contact arm and to dissipate the kinetic energy of themoving parts in relative sliding movement of said contacts and inelastic strain of said contact arm in a direction having no substantialtendenc to reopen said contacts.

tact arm and said inertia member in unison, and

means for moving said contact arm and said inertia member together froma contact breaking to a contact making position, said resilient mountingmeans for said inertia'member being arranged to permit appreciable freeovertravel of said inertia member with respect to said contact arm afterengagement of said contacts therebyto cushion the impact of saidcontacts by converting the kinetic energy of said contact arm andinertia member into elastic strain having no substantial tendency toreopen said contacts.

9. An electric contact making and, breaking device comprisingcooperating switch contacts, a contact arm movably mounted at one end tocontrol one of said contacts, an inertia member having a substantialmass in relation to the mass of said arm, means including resilientmeans between said inertia member' and said arm for mounting saidinertia member upon said arm for appreciable free arcuate movement withrespect to said arm, and means for simultaneously moving said contactarm and said inertia member from contact breaking to contact makingpositions, said resilient means permitting continued movement of saidinertia member relative to said arm after said contacts are engagedthereby to convert the kineticenergy of said member and said am intoelastic strain having no substantial tendency to reopen said contacts.

10. An electric contact making and breakin device comprising cooperatingswitch contacts. a contact arm movably mounted at one end to control oneof said contacts, an inertia member of substantial mass in relation tothe mass oi said contact arm, means including a resilient member formounting said inertia member upon said arm for appreciable tree arcuatemovemen of said member with respect to said arm, and means forsimultaneously moving said contact arm and saidinertia member about.said one end of said-arm from a contact breaking position to a contactmaking position, said resilient mountin: means being arranged to permitappreciable said contacts.

overtravel of said inertia member but to change its path of travel atterengagement of said con-- tact: thereby to cushion the impact of said contact: by converting the kinetic energy of said contact arm and inertiamember into elastic strain having no substantial tendency to reopenALLEN G. STIMSON.

